35. The Tiffanian Land-Mammal Age (Middle and Late Paleocene) in the Northern Bighorn Basin, Wyoming

Author(s): Ross Secord

Publication 35


The Tiffanian North American land-mammal age is an informal biochronologic unit that spans 4.5
myr of the middle and late Paleocene. It is preceded and succeeded by the Torrejonian and Clarkforkian land-mammal ages, respectively. The Tiffanian was initially based on a small collection of mammals from southern Colorado, but faunas of Tiffanian age are now known throughout the Rocky Mountain region. The richest and most complete sequence of middle and late Tiffanian faunas known occurs in the northern Bighorn Basin. These faunas are the primary basis for regional Tiffanian biochronology. The Bighorn Basin sequence is also important because it preserves the only known detailed record of faunal change across the Tiffanian-Clarkforkian boundary, which is marked by the first appearance of rodents in North America. Geomagnetic polarity reversals, a carbon isotope excursion marking the Paleocene-Eocene boundary, and a recent Ar40/Ar39 age from a volcanic ash provide a strong geochronologic framework for the faunal sequence. Thus, this record affords a unique window into the evolution of North American mammals that can be compared globally with other biotic, paleoecological, and paleoclimatic records. (Go to the link and see more of this paper.)

Publication Information:

Publisher: University of Michigan

Month of Publication: December

Year of Publication: 2008

Location: Ann Arbor, MI

Volume Number: 35

# of Pages: 193